Cymbites Calcite Ammonite Fossil Black Ven Marls Lower Lias Jurassic Coast Black Ven Lyme Regis Dorset UK

Description

Authentic Cymbites Calcite Ammonite Fossil

This beautiful Cymbites Calcite Ammonite Fossil is an exceptional genuine specimen from the Black Ven Marls, Lower Lias Formation, collected along the world-famous Jurassic Coast at Black Ven, Lyme Regis, Dorset, UK. Formed during the Early Jurassic period (approximately 195–200 million years ago), this fossil is a fine example of the genus Cymbites, known for its elegantly smooth whorls and distinctive calcite preservation.

Your specimen was discovered by our team members, Alister and Alison, on 13 September 2025, and has been expertly cleaned, prepared, and treated by Alison to reveal its remarkable natural beauty. The photographs show the exact fossil you will receive, chosen for its exceptional condition and quality.

Geological Context and Origin

This ammonite originates from the Black Ven Marls Member of the Charmouth Mudstone Formation, part of the Lower Lias Group — a famous fossil-bearing sequence exposed along the UNESCO World Heritage Jurassic Coast. The cliffs of Lyme Regis and Charmouth are among the most fossil-rich deposits in Europe, celebrated for their abundant ammonites, belemnites, and marine reptile remains. These sediments were deposited in a calm, offshore marine environment, consisting of fine muds and silts laid down under low-oxygen (anoxic) conditions, which limited decay and allowed for exceptional fossil preservation.

Over millions of years, mineral-rich groundwater replaced the original aragonitic shell material with calcite, producing the translucent crystalline appearance characteristic of fossils from this region. The fossil-bearing layer belongs to the Sinemurian Stage of the Lower Jurassic and is associated with the Cymbites biozone, an important ammonite zone used by geologists for stratigraphic correlation across Europe.

Scientific Classification

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Subclass: Ammonoidea
• Order: Ammonitida
• Superfamily: Psiloceratoidea
• Family: Cymbitidae
• Genus: Cymbites
• Age: Early Jurassic (Sinemurian Stage)
• Formation: Black Ven Marls, Lower Lias
• Locality: Black Ven, Lyme Regis, Dorset, UK

The genus Cymbites is distinctive among early Jurassic ammonites, known for its smooth shell surface and simple suture lines. It is a significant index fossil, helping scientists identify and correlate Early Jurassic rock strata worldwide.

Morphological Features and Preservation

This Cymbites Calcite Ammonite displays a nearly complete shell with the classic discoidal, evolute coiling pattern typical of the species. Unlike more heavily ribbed genera such as Promicroceras, Cymbites is characterised by smooth, gently curved whorls, a broad outer venter, and a wide umbilicus, giving it an elegant, open spiral appearance. The fossil has been perfectly preserved in pale golden calcite, with fine internal crystallisation creating a natural sheen and translucence under light.

Calcite infill reveals delicate details of the original shell chambers, showing the internal structure of the phragmocone where the ammonite once controlled its buoyancy. The surrounding marlstone matrix provides excellent contrast, enhancing the visual presentation of the fossil. This specimen has been professionally stabilised to maintain integrity while preserving its natural surface finish.

The scale cube (1 cm) shown in the photographs provides an accurate size reference, and full measurements are included in the listing images.

Palaeobiological and Scientific Importance

Ammonites such as Cymbites were marine cephalopods, related to modern squids and nautiluses. Their coiled shells were divided into chambers filled with gas and fluid, allowing for buoyancy control as they swam in the open seas of the early Jurassic. Cymbites is part of one of the earliest post-extinction ammonite lineages, appearing shortly after the Triassic–Jurassic mass extinction event, which drastically reshaped marine ecosystems.

This fossil represents a critical evolutionary stage, showcasing the early diversification of ammonites that would later dominate the oceans for over 150 million years. The smooth, hydrodynamic shell design of Cymbites suggests it was an agile swimmer, well-adapted to open marine environments where it likely fed on small crustaceans and plankton.

Calcite-preserved examples such as this one are particularly sought after because they demonstrate both the aesthetic beauty and scientific significance of fossilisation. They reveal how biological remains can be transformed into crystalline forms while retaining the exact structure of the original shell, offering a fascinating glimpse into ancient life and geological processes.

Authenticity and Provenance

All of our fossils are 100% genuine specimens and come complete with a Certificate of Authenticity. Each piece is responsibly collected, carefully cleaned, and professionally prepared to ensure authenticity and preservation. We never sell replicas or artificially enhanced specimens — the fossil shown is the actual piece you will receive.

This Cymbites Calcite Ammonite Fossil from Black Ven, Lyme Regis, Dorset is a superb representation of the Early Jurassic marine world and a timeless addition to any fossil collection, combining natural geological artistry with scientific heritage from the iconic Jurassic Coast of the United Kingdom.